As it is known, many pourable food products, such as fruit juice, milk, tomato sauce and beverages in general, are sold in a wide range of containers of different types and sizes, such as: parallelepiped-shaped packages made of multilayer, plastic- and/or paper-based, laminated materials or so-called multilayer cardboard materials; beaker-shaped plastic packages; blow-molded bottles; or glass, sheet metal or aluminium containers.
All these containers are fitted with closures which can be opened to allow access by the consumer to the food product, either to pour it into a drinking vessel or consume it straight from the container.
Screw cap closures are commonly used on bottle-type containers, whereas containers made of multilayer cardboard materials are often simply provided with tear-off markers, or with pour openings formed in the containers and covered with pull tabs.
Containers made of multilayer cardboard materials are also known to be fitted with plastic closures injection molded directly onto the containers, about openings formed through the packaging material, so as to completely close and seal the openings. Closures of this sort normally define the pour opening of the container, which may be fitted, for example, with a screw or snap cap.
Another type of container is also known which comprises a main portion made of multilayer cardboard material, and a top, for pouring the liquid or pourable product in the container, made of plastic material and produced by blowing a plastic tubular preform or by thermoforming or even by other suitable forming techniques, such as compression or injection molding.
An example of a plastic top for this type of containers is illustrated in international patent application No. WO2008/148764.
In this case, the plastic top basically comprises a pouring spout, defining the pour opening by which to pour the food product out of the container, and a cylindrical cap fitted to the pouring spout in a removable way.
The pouring spout may have one layer of gas- and/or light-barrier material, e.g. EVOH, and is produced, and attached to the container, in a closed configuration. In particular, the pouring spout comprises a substantially cylindrical tubular neck defining the pour opening and a cover portion integral with the neck and closing the pour opening.
More specifically, the neck has a bottom open end adapted to be attached to the container and a top end closed by the cover portion and provided with a weakening line, along which the cover portion can be detached from the neck when the container is opened by the user for the first time.
The cap is formed by an annular cylindrical lateral wall, which has an internal thread for engaging a corresponding thread provided on an outer lateral surface of the neck, and by a disk-shaped top wall for covering, in use, the top of the pouring spout.
In order to obtain the detachment of the cover portion from the neck, the lateral wall of the cap is provided with opening promoting means arranged for engaging further opening promoting means of the cover portion upon removal of the cap from the pouring spout to separate the cover portion from the neck along the weakening line.
In particular, according to one of the embodiments illustrated, the opening promoting means are defined by tab means having an end hinged to the lateral wall of the cap and an opposite end arranged for interacting with the further opening promoting means; the tab means may comprise a plurality of distinct tabs or a continuous tab extending through the whole circumference of the neck.
Alternatively, the opening promoting means may comprise hook means projecting inside the cap.
In both cases, the further opening promoting means for cooperating with the tab or hook means comprise an annular rim of the cover portion radially protruding outwards so as to form an abutment surface transversal to the axis of the pouring spout.
The first opening of the container is accomplished by rotating the cap around its axis; thanks to the interaction of the threads, the cap is advanced along a stroke comprising a rotational component about its axis and a translational component along the same axis.
During this movement, the tab or hook means of the cap contact the protruding rim of the cover portion and slide therealong according to the pitch of the threads so exerting a lifting action on such rim for producing the detachment of the cover portion from the neck at the weakening line.
This kind of solution requires an extended sliding interaction between the tab or hook means and the protruding rim to obtain opening of the neck; the consequences are a relatively high friction of the surfaces into contact and a too large effort required to the user to reach the appropriate level of tension in the plastic material to obtain fracture.